Radio frequency identification (RFID) is a methodology that can be employed for tracking of goods in supply chains. Some RFID systems are configured as a passive system. Others may be configured as an active system. Passive RFID systems are preferred for a number of applications because such systems tend to have a lower cost as compared to active RFID systems. For passive RFID systems, a RFID tag that is to be read by a reader often has an antenna that has a small electrical size. Single resonance RFID antennas have a resonance near the center of the operating band. In particular, this operating band is either the 868 MHz band, or the 915 MHz band, or both of these bands. For many RFID tag antenna designs, this small size and frequency range is desired due to design criteria that requires the tag antenna's input impedance to be a conjugate match to that of the chip to which it is connected, and the chip typically has a small resistance and a moderate capacitive reactance.
Such impedance matching can be a difficult design problem for an RFID tag antenna that is to be used in a system in which the RFID tag may be worn by, attached to, or on a human body or other animal body. The difficulty with such impedance matching can contribute to a small read range for readers of such RFID tags that may be worn by or, attached to, or on an animal (e.g. a human, a dog, a farm animal, etc.).